I'm pretty sure gray knobs were specific to the 60-61 GMC's, but I am not an expert so I am just restating what I've seen and read here and elsewhere.
(please correct me if I'm wrong)
Anyway I picked up a few more knobs; two for the factory radio and a gray knob cigarette lighter. Luckily I kept the gray single-speed original wiper knob, so I have that too.
I have gray everything else; Vents/Choke and am just missing the gray HEAT knob from the heater
Here are a few photos and you can see the gray either looks darker or lighter depending on the light. I am replacing the chrome-ring type which I think are Chevy truck but am not sure.
*TRIVIA
There is another item that was in my Suburban when I purchased it back in 2007. Preliminary research tells me it may be from the 40's or 50's.
It's the Bird-Beaked looking item in the photo....Is it a can opener or picnic cheese shredder or moustache comb?......What is it's purpose?